This question has been bugging me ever since I've started learning usability.

I am talking about the two buttons for the flush : Full and half container.

On one hand, the button shape has to represent its function. Thus a bigger button must mean the full container.

On the other, dangerous/heavy process triggers should be protected from being triggered by mistake and generally harder to trigger(If you press it, you mean it). From that point of view, the full container button should be smaller and further from the user and the half-container should be big and easy to reach/press.

Also, keep in mind, that I come from a country where water is scarce. So people are educated and encouraged from a very young age to conserve. But it's also a rising trend worldwide now...

While observing these interfaces all over the world, I didn't see any consistency in the matter. The buttons really go both ways. Sometimes the full container is the big one and sometimes it's the small one. It is inconsistent even within the country. I've also seen all kinds of unconventional designs. But again, nothing clear and intuitive from the moment you see it...

What are your thoughts on the matter? Have you ever seen a good, clear design, that is really intuitive? Do you know of any standards for this?

NOTE: Please don't suggest text as a solution. Icons may be interesting. But I've never seen a clear icon for that.

Well, it would not be too hard to find icons for "poop" and "pee", but would you really want to see such icons? Imo the small and large buttons are perfect. You can enhance the UX by putting the 2 buttons on top of each other where the topmost is the small one, which further indicates that you will only be emptying part of the container. See cdn12.grohe.com/~mi/1327/1999/…
–
Bart GijssensJul 29 '14 at 10:02

2

Well, there's the obvious issue with your icons suggestion. Although it might prove effective. But the image you've posted is the exact thing that I'm talking about! What does the top button stand for? Is it the full or the half? I've seen many designs implement some version of that, while the small button is also providing more resistance to push and it's the full container. You can switch the placement. But it would still not be clear. Plus, the bottom one is harder to reach. Especially for tall people.
–
BoranasJul 29 '14 at 10:09

3

I have a two-button toilet. The buttons are two parts of a circle and are nearly the same size. I have no idea what they mean, so I always press both at once.
–
BoannJul 29 '14 at 17:43

10

I can't be the only one who thinks a kickable UI would be much preferable to a digital/manual one. God knows what people do with their hands in there.
–
BinaryTox1nJul 29 '14 at 20:38

2

This question kept playing on my mind for some time now too. I exactly asked myself: Is the big button the big flush or the flush supposedly used more often? The only way I could find out is the empiric way. Sadly I found out that it's not even standard. Most of the times the big button is the big flush but a few times it's the other way around.
–
André StannekJul 30 '14 at 6:52

20 Answers
20

Because litres are a unit used everywhere across the world, a non-language dependent text solution is to label the amount of water used. Typically the symbol "L" is recognised as litres in almost any scenario.

Here is an example:

In addition, the two labels could be used as "wave to flush" sensors, if spaced far enough apart, preventing the spread of germs in public restrooms.

Labelling the amount of water use in clear sight provides the benefit of educating users on water conservation. Anybody who uses a toilet with these buttons frequently could quickly respond to how much water a toilet uses.

"Because litres are a unit used everywhere across the world" -> Is this true? Aren't Americans still using gallons?
–
Bart GijssensJul 30 '14 at 7:59

8

@BartGijssens North Americans are still taught to use gallons and other US customary units, but packaging does list SI units in many cases. Also note, a US gallon is not the same as an imperial gallon (sometimes used in countries such as Canada, England, Scotland and Wales), there's almost a litre difference between them.
–
PharapJul 30 '14 at 8:05

34

@BartGijssens We buy gallons of milk and wine, but 1L and 2L of carbonated soft drinks, and 1.5L of liquor. And, despite our apparent lack of education (e.g. only half of high school graduates can read their own diploma), I'm pretty sure most Americans know that 3 is less than 6.
–
phyrfoxJul 30 '14 at 13:20

3

My comment was not so much about understanding that 3 is less than 6, but mostly to the L abbreviation. If not everyone understands what it means, a user may probably not even understand that the button is a flush button. I have no clue if everyone in the world knows the L unit.
–
Bart GijssensJul 30 '14 at 13:43

3

@smpl You're right about the wine. I checked. I could have sworn it was in gallons. I guess we don't really always even pay attention to what we're buying!
–
phyrfoxAug 1 '14 at 5:23

Good find :) Yes, that I believe is most universal way how to address this issue, completely disarming the translation problem.
–
Harijs DeksnisJul 29 '14 at 11:55

1

It looks like the images were added after the installation, due to the confusion. Seems to me, that it should be a combination of imagery and shape. What do you think? Also, I don't recall seeing these in the wild. Do you know where is it from(which country)?
–
BoranasJul 29 '14 at 12:42

@Boranas Yeah, they seems to be added (especially the second droplet image). I don't know where they're from as I've grabbed them from google on random websites. But the idea is there: adding icons make it easier and users know what the different buttons do.
–
refreshfrJul 29 '14 at 13:11

I think a lot of people wouldn't take the effort to try to understand the color labeling and simply press a random button.
–
ChristianJul 29 '14 at 10:35

7

I think that the main issue with this type of solutions is that it makes a decision for you. It switches the scope from "let's not waste water" to "what did I do and what to do with it"...
–
BoranasJul 29 '14 at 12:25

51

You are violating one of the basic laws of usability: You should not rely only on colour. Documentation: sitepoint.com/cant-rely-color and an article from Usability expert Jakob Nielsen which I seem not able to find now.
–
sergiolJul 29 '14 at 14:13

Yeah. I've seen these. But I don't remember them to be obvious. There are always issues of visibility, like dim light. But I do agree that this eliminates the confusion when you pay attention.
–
BoranasJul 29 '14 at 12:34

1

This example, if they are embossed markers is probably useful for using in the dark too (a common use for toilets, I imagine).
–
JonW♦Jul 29 '14 at 13:01

2

You can always have this design with colored dots (blue, gray, whatever), and having non-flat buttons is useful as you can feel it with your fingertips: blind-friendly (?) and "wake-up-in-the-night-and-don't-want-to-turn-the-light-on"-friendly
–
refreshfrJul 29 '14 at 13:15

3

I really support the point for the sight impaired. But I'm not sure that you want to finger the buttons in a public toilet for too long...
–
BoranasJul 29 '14 at 13:25

That works and probably also conserves the most water. Because nobody wants to stand there more than required. But that also poses the usability issue - you must be physically present for the whole duration.
–
BoranasJul 29 '14 at 16:03

6

@Boranas: Maybe when they stay and see their remains, they will finally start using the toilet brush. ;)
–
Christian StrempferJul 29 '14 at 16:06

3

A system like this may be confusing to the user. A user should never even have to question how to flush the toilet.
–
smplJul 30 '14 at 3:54

2

@smpl: This is the simplest solution. They don't have to choose between different buttons, there is only one direction to press. Why do you think this is confusing?
–
Christian StrempferJul 30 '14 at 5:03

2

@unor: Or else they push the button briefly to the tactile stop, get a wimpy flush, again push the button briefly to the tactile stop, get another wimpy flush, and maybe try a third time before mumbling about how some companies can't even make a toilet that works properly.
–
supercatAug 3 '14 at 22:06

A google image search for toilet flush buttons brings up a surprising variety of designs. I didn't realise there were so many!

I reckon the small and large buttons representing small and large flushes respectively are the best. And then couple this with separating the buttons apart so that the large one is not easily pressed when you try to only press the small one.

e.g.

And then if icons were imprinted on top of these too e.g. large/small droplets then that may help further distinguish what they are.

You push it half way to the right for a little flush and all the way to the right for a big flush. A Big flush would be more work, as you have to push the slider all the way to the right.
If the Slider has an Arrow-Shape and there is a small drop half-way and a big Drop on the right, it would be easy to understand.

Since some people said many people will just push with random violence against the slider and get it all the way to the right, because stopping halfway is cumbersome and needs concentration, here a mechanical help: The construction could feature a damper/mechanical resistance, so your first push would stop at the small flush and you have to increase the push more to get all the way to the right...

It might be worth noticing, depending the on the design on the slider, it might be hard to push. E.g. someone with weak fingers (which might be able use an elbow on a large enough button), on maybe more commonly, users with long fingernails might have problems inserting their fingers far enough to get a good grip. I.e. sliders of this kind should err on the side of bigness, to allow for that.
–
zrajmJul 29 '14 at 15:46

2

+1. Great, intuitive concept. This is more natural because this is already how faucets work. And I think there are ways to make this concept usable by people with weak fingers, too.
–
RyanJul 29 '14 at 19:51

10

Mind that Apple may have a patent on this ;)
–
Bart GijssensJul 30 '14 at 7:56

@zrajm I would probably not use a flat slider, but one with a raised edge which you can easily grab and move with your whole hand! Like the slide locks on old barn and toilet doors
–
FalcoJul 30 '14 at 8:00

1

I would think a big flush would be less work, regardless of a click. You go to the bathroom, finish, and smack the thing to flush, likely pushing it all the way to the stop out of just wanting to get the job done; it's too menial and common a task to warrant any kind of thought from many people, I think. Just like a faucet; how many times have you simply turned a handle-faucet all the way on by just applying an arbitrary amount of force to it, or a knob faucet to some random location because you just want the water to be on for a moment? I would do left=>big and right=>small or something.
–
Jason CJul 31 '14 at 7:43

@Chris, yes, mainly because the toilets were included as part of a 'green' building and all its bathrooms had pretty obvious signs explaining the lever. The image I found doesn't really do the actual handles justice; at least to me, the icons seemed decently-sized.
–
AlexJul 30 '14 at 13:22

The text may make it even more confusing to non-english speakers.
–
smplJul 30 '14 at 17:01

+1 I support the text, because two-button toilets are completely foreign to me and it took me at least three or four trips outside the USA to figure out what was going on with them, despite various icons and symbols.
–
Jason CJul 31 '14 at 7:31

Another American who supports the text. Most users I’ve spoken with are unaware of the difference between the buttons, and in some cases haven’t even noticed that there are two options. They both flush the toilet, so the difference is very subtle from the user’s perspective, and while you can get an ‘Aha!’ from people by explaining it, they really do need that first explanation. Any options for someplace where this type of toilet is new or rare need to take this into account. If most of your users speak English, an option like this will reach people who wouldn't even think about the icons.
–
KarenJul 31 '14 at 13:46

Many researchers have shows that Icons are hard to memorize. Without training or prior experience they may not be easy to interpret. Especially for people with cognitive disabilities, text with an icon makes it much more accessible. In my opinion, maximum usability can be achieved by minimizing cognitive load.
–
Usman.AJul 31 '14 at 16:31

Among those I have seen, I prefer the "small droplet" <-> "large droplet" one. If I want much water, I press the large droplet. If I want less water, I press the small droplet. (Both buttons are equally sized.)

Have you ever noticed how questions about toilets always make it to the hot questions list? :)

Anyway, the best option I see would be to have two buttons like this:

First of all, the buttons are equal size, so that isn't confusing. Also, it has water droplets on it so someone can see the right button will give more water. If you make it large enough, the blue water "waves" will give the user a quick indication without a lot of mental activity.

Curious what the little "tab" is there for? (It's the little red squiggle over the left button) I think that might be a good idea for a user. If they push the right button, it'll technically push down both buttons. If they push down the left button, it would push down only one button. I don't know if users would appreciate this, but it might be only logical that if they push half of the buttons, they get half of the water. I'd say do a little more research (especially with younger children) to see if they get this or not before implementing this.

Take the decision out of the hands of users. Have one button but make the toilet smart based on level of displacement, it wouldn't need an electronic sensor, just a better designed bulb in the reservoir right? Or possibly an extra pressure tube similar to how a barometer works? As the toilet is filled higher and with denser material the physical pressure of that mass should dictate how much water is used. For special cases they may need to flush twice.

Not making a claim on the UX suggestion, but the assumptions on how to engineer this are wrong. Bulb in the reservoir measures the water level in the reservoir, and is unrelated to the contents of the bowl.
–
Mr.MindorAug 1 '14 at 22:02

Also the water level in the bowl can give no indication of the density of the contents. Most toilets work on gravity pushing then pulling the water through the S trap (see shape of which in icons of totymedli's answer.) As anything enters the bowl, it will fill to the point the water reaches the top of that loop, and starts trickling down the other side. If water enters the bowl fast enough (as in a flush) water passes over the top fast enough to fill the entire cross section of other side of the tube creating a siphoning effect which pulls the rest of the water (and contents) with it.
–
Mr.MindorAug 1 '14 at 22:09

unless clogged, the water level will not go beyond that point to rise regardless of the cause.
–
Mr.MindorAug 1 '14 at 22:15

You would have to setup a flowmeter in the S trap. I wonder if the material cost would be worth it?
–
Wayne WernerAug 5 '14 at 3:55

So yes, it sounds like it wouldn't be in the reservoir but the question for me was more around possibilities of making smarter toilets instead of multiple buttons. Thanks Mr.Mindor, that sounds like it is a tricky problem.
–
Mark SloanAug 19 '14 at 0:16

Buttons are not a good UI when the operator is likely to have soiled hands when using them. Auto-flush toilets have existed for many years now, and the technology is both cheap and mature. The only barrier to adoption is patents and the common requirement that bathrooms have minimal electrical wiring.

I think Falco's answer is a good start, but the general idea could also work with the existing lever design: push the lever half-way for a "light" flush, or all the way for the full flush. The lever should take a bit more force to complete the full flush so that people don't unwittingly always push it as far as it will go.

Since the feedback is occurring in real-time, the user will instantly know if the flush was, ahem, insufficient. And in that case, a natural response is to push the lever again, but harder.

If you wanted to let folks know exactly what was happening, you could post a diagram on the wall showing the lever depressed half-way with one drop of water beside it, and fully depressed with three drops of water beside it.

There's a trend in the US to get rid of the handles and buttons completely. Sensors determine when the person has moved and auto flush. Sinks dispense water while hands are under the faucet and dryers auto turn on.

Pretty much the only thing left in a bathroom to physically touch is the door on the way out. Which, ultimately, is why I prefer single dispense paper towels over air dryers. Seems to me that the best thing for humans is to have as little contact as possible in that room.

I just don't think there is a good water use case that would require the user to pick from 2 different flush settings. As the designer, pick the smaller one. If it's not enough, a second flush should take care of whatever was left. If it doesn't then you probably need to look at your toilet design anyway.

Also, I've seen several places with urinals that do not require flushing. I haven't bothered to look into how that works or whether it's better/worse for the environment but it certainly represents another approach.

Off topic - but there are some sensor loos wich I use: the problem is that the sensor looks like a button, so there is a tendency for users to try to touch the sensor - which obviously totally undermines the point of a 'no touch' means of activating the loo / sink
–
PhillipWAug 5 '14 at 20:46

@ChrisLively Didn't find anything about two modes. There's almost nothing about actual toilet sensors. Most of them are urinals. The ones that are actually toilets have one mode only.
–
BoranasAug 7 '14 at 8:12

One button should be fitted which is the water saving option and then if the user finds that this is insufficient a second flush (within a certain time period) should then produce a larger flush of water.

UPDATE

Bearing in mind the comments below I'd modify my suggestion to one button which can be just pressed as needed: short (small distance down) press down for small amount of water, longer (further depression) press for larger amount of water. So one button with a two stage action.

From the users perspective it is not so great experience. First, you have to wait a certain time (which will add up to hours, even days, over the lifetime since we use the lavatory many times), second, you have to look at whatever you left there and see whether the water amount is enough to flush it away and then make further choices. I think people want to be done with it as soon as possible and get to washing their hands as soon as they press the button first time.
–
Harijs DeksnisJul 30 '14 at 9:41

4

Secondly, a large flush means a greater pressure. This is some times needed to clear the can, and is not fascilitated by two smaller flushes.
–
NixJul 30 '14 at 17:35

We have "efficient" flush toilets. And there are times (not sayin' who) that even 3 or 4 flushes aren't enough.
–
Wayne WernerAug 5 '14 at 3:57

Public restroom users would never take the time to 'check' and re-flush. They hit the button and are gone. Leaving the unpleasants to the next user. :)
–
Joshua DanceAug 5 '14 at 15:42

Acoustic sensor in the u-bend that detects the density of the deposit you have made using pulses of sound. Place a single button to trigger a flush. The on board computer can then detect a #1 or #2 and flush accordingly. Computer then charges battery using a water wheel.

I find toilet buttons a huge design flaw because after nearly two decades of toilet usage I have to find out the truth from a question in User Experience.

I always tried to find out why there are two buttons and what the size means. I thought one button empties all the tank and the other button flush water as long as I press it, because sometimes I really just need a little flush. Never mind, after I tried it I realized I am wrong.

Icons make it totally understandable, so I mixed a few answers here to create the one solution which I think is the best.

The colour and text concepts... priceless!
I believe the visuals which show a lot of information regarding water level and toilet shape are too much. This is definitely somewhere you need to have simple and elegant design language.

The button I see most often is akin to a Yin-yang symbol. One slightly smaller than the other.

Getting across the amount of water used is obviously the main attribute here and this can be done so simply. Here is my suggestion for an elegant solution, the same methodology is used on many things. (for example, air flow on a hairdryer)

One would argue that the smaller button should be the full tank(and have the 3 waves). In any case, this type of design has been discussed several times here. There are mechanical issues with it. Namely, the small button gets tangled with the big one and both are pressed always. This is partially due to the design itself. The buttons are too small for the wire-up behind it.
–
BoranasAug 5 '14 at 9:43

The technical issues I have found is that they don't use a robust enough plastic, there are effectively stalks of plastic which protrude through narrow holes into the cistern, these stalks need to be fatter or just a more robust ABS.
–
Marty DunlopAug 5 '14 at 15:04

This was mentioned by the OP in the question. The full tank should be harder to press (perhaps smaller) because it is the most expensive action.
–
Joshua DanceAug 5 '14 at 15:43

I believe that if the full flush was the smaller button, that would draw users to utilise the larger button more because of it's size (in most cases, all that is needed (on a ratio of 2:1 for leak and drop)). Yet this would be an easy enough change to adapt to because you understand, to complete the expensive task, it should be harder to initiate. Take for instance a reset button on a gameboy, it's tiny and hidden so as not to initiate accidentally as it is costly.
–
Marty DunlopAug 7 '14 at 11:52